Bio-based Magnetic Fe3O4/SiO2@SA Composite Beads for Efficient Removal of Methylene Blue from Water

Dye wastewater pollution has become a significant environmental issue threatening aquatic ecosystems and human health. To achieve green and efficient removal of organic dye (e.g., methylene blue (MB)), bio-based magnetic composite beads (Fe 3 O 4 /SiO 2 @SA) were prepared through HCl-assisted SiO 2 extraction, co-precipitation and ion-crosslinking under mild conditions, without high pressure, high reaction temperature or toxic chemicals. Batch adsorption studies of MB were used to explore the adsorption performance and mechanism of Fe 3 O 4 /SiO 2 @SA. The experimental results demonstrate that the MB removal rate of Fe 3 O 4 /SiO 2 @SA composite beads reaches 91.75% under optimised adsorption conditions (25 ℃, pH 9, 100 mg/L initial MB concentration, 20 mL solution volume, and 10 mg adsorbent dosage). Compared to Fe 3 O 4 and Fe 3 O 4 /SiO 2 powders, the adsorption capacity is much higher at 183.77 mg/g. Physisorption and monolayer adsorption were demonstrated. The optimal adsorption capacity of Fe 3 O 4 /SiO 2 @SA on MB is 1918.65 mg/g. In addition, Fe 3 O 4 /SiO 2 @SA enabled rapid and efficient solid-liquid separation through an external magnetic field and exhibits excellent reusability. The removal efficiency stayed at 80.1% after six cycles of adsorption and desorption, and reached 81.1% in river water. The Fe 3 O 4 /SiO 2 @SA composite beads possess excellent adsorption capability, rapid magnetic separability and good reusability, providing a sustainable solution for dye water treatment. This research provides novel viewpoints and experimental supports for the evolution of low-cost, recyclable, environmentally friendly adsorbents.